实体类、数据访问类、属性扩展

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 实体类_数据访问类.App_Code
{
    public class Users
    {
        private string _username;
        //封装
        /// <summary>
        /// 用户名
        /// </summary>
        public string username
        {
            get { return _username; }
            set { _username = value; }
        }

        private string _password;
        /// <summary>
        /// 密码
        /// </summary>
        public string password
        {
            get { return _password; }
            set { _password = value; }
        }

        private string _nickname;
        /// <summary>
        /// 昵称
        /// </summary>
        public string nickname
        {
            get { return _nickname; }
            set { _nickname = value; }
        }

        private bool _sex;
        /// <summary>
        /// 性别
        /// </summary>
        public bool sex
        {
            get { return _sex; }
            set { _sex = value; }
        }
        //属性扩展，可以再添加一个方法，把性别转换成字符串类型，打印时直接u.sex1，不用再在program里面每次单独转换
        public string sex1
        {
            get { return (_sex ? "男" : "女"); }//只读取，不能填写或改写
        }

        private DateTime _brithday;
        /// <summary>
        /// 生日
        /// </summary>
        public DateTime brithday
        {
            get { return _brithday; }
            set { _brithday = value; }
        }
        //属性扩展
        public string brithday1
        {
            get { return _brithday.ToString("yyyy年MM月dd日");}
        }

        private string _nation;
        /// <summary>
        /// 民族
        /// </summary>
        public string nation
        {
            get { return _nation; }
            set { _nation = value; }
        }
        //属性扩展
        public string nationname
        {
            get 
            {
                NationData ndata = new NationData();
                string end = ndata.select(_nation);
                return end;
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;

namespace 实体类_数据访问类.App_Code
{
    public class UsersData
    {
         //调用数据连接类、数据操作类
        SqlConnection conn = null;//等于null，不占空间
        SqlCommand cmd = null;

        //构造函数
        public UsersData()//构造函数名称与类名一致
        {
            conn = new SqlConnection("server=.;database=Data0720;user=sa;pwd=123;");
            cmd = conn.CreateCommand();
        }

        //添加
        /// <summary>
        /// Users表添加方法
        /// </summary>
        /// <param name="u">要添加到数据库中的Users对象</param>
        public void Insert(Users u)//有实体类，括号内的参数把实体类的对象放进去
        {
            cmd.CommandText = "insert into Users values(@a,@b,@c,@d,@e,@f)";
            cmd.Parameters.Clear();//一定要先清空
            cmd.Parameters.Add("@a", u.username);
            cmd.Parameters.Add("@b", u.password);
            cmd.Parameters.Add("@c", u.nickname);
            cmd.Parameters.Add("@d", u.sex);
            cmd.Parameters.Add("@e", u.brithday);
            cmd.Parameters.Add("@f", u.nation);

            conn.Open();
            cmd.ExecuteNonQuery();
            conn.Close();

        }

        //查询（一条信息）
        /// <summary>
        /// Users表查询方法
        /// </summary>
        /// <param name="Uname">查询数据库中的Users信息表</param>
        /// <returns></returns>
        public Users select(string Uname)
        {
            Users u = null;
            //查
            cmd.CommandText = "select * from Users where username=@a";
            cmd.Parameters.Clear();
            cmd.Parameters.Add("@a",Uname);

            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                dr.Read();
                u = new Users();
                u.username = dr["username"].ToString();
                u.password = dr["password"].ToString();
                u.nickname = dr["nickname"].ToString();
                u.sex = Convert.ToBoolean(dr["sex"]);
                u.brithday = Convert.ToDateTime(dr["brithday"]);
                u.nation = dr["nation"].ToString();
            }
            conn.Close();

            return u;
        }

        //删除
        /// <summary>
        /// Users表删除方法
        /// </summary>
        /// <param name="Uname">删除数据库中的Users信息表中的信息</param>
        public bool Delete(string Uname)
        {
            bool delok = false;

            cmd.CommandText = "delete from Users where username=@a";
            cmd.Parameters.Clear();
            cmd.Parameters.Add("@a",Uname);
            
            conn.Open();
            try//验证、判断是否删除成功，有可能是数据库服务没开，服务器连接不上，这样不可以返回删除成功
            {
                cmd.ExecuteNonQuery();//如果没执行成功，程序报错，用try包起来
                delok = true;
            }
            catch { }//让catch捕获住错误，不让程序崩溃，执行delok = false;，这个是一开始设置的默认的，所以catch可以空着
            //finally//必须走，
            //{
                conn.Close();//这一步必须走，finally可写可不写
            //}

            return delok;
        }

        //修改
        /// <summary>
        /// Users表修改方法
        /// </summary>
        /// <param name="u">修改数据库中的Users信息表中的信息</param>
        public void Update(Users u3)     
        {
            cmd.CommandText = "update Users set [password]=@b,sex=@d where username =@a";
            cmd.Parameters.Clear();
            cmd.Parameters.Add("@b",u3.password);
            cmd.Parameters.Add("@d",((u3.sex==true)?"1":"0"));
            cmd.Parameters.Add("@a",u3.username);

            conn.Open();
            cmd.ExecuteNonQuery();
            conn.Close();
        }
        
        //查询所有信息

        public List<Users> select()//用泛型集合，不规定个数，单数固定类型都得是Users类型,放置所有Users数据对象
        {
            List<Users> list = new List<Users>();
            cmd.CommandText = "select * from Users";
            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)//如果数据表中有数据
            {
                while (dr.Read())//循环读取全部数据
                {
                    //每读取一行数据，就只做一个Users对象
                    Users u = new Users();
                    u.username = dr["username"].ToString();
                    u.password = dr["password"].ToString();
                    u.nickname = dr["nickname"].ToString();
                    u.sex = Convert.ToBoolean(dr["sex"]);
                    u.brithday = Convert.ToDateTime(dr["brithday"]);
                    u.nation = dr["nation"].ToString();

                    //在循环中，把制作好的每一个对象都放到集合中去
                    list.Add(u);
                }
            }
            conn.Close();
            return list;
        }




    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 实体类_数据访问类.App_Code
{
    public class Nation
    {
        private string _nationcode;
        public string nationcode
        {
            get { return _nationcode; }
            set { _nationcode = value; }
        }


        private string _nationname;
        public string nationname
        {
            get { return _nationname; }
            set { _nationname = value; }
        }
    


    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;

namespace 实体类_数据访问类.App_Code
{
    public class NationData
    {
        SqlConnection conn = null;
        SqlCommand cmd = null;
        public NationData()
        {
            conn = new SqlConnection("server=.;database=Data0720;user=sa;pwd=123;");
            cmd = conn.CreateCommand();
        }
        public string select(string code)
        {
            string end = "<无>";
            cmd.CommandText = "select * from Nation where nationcode=@a";
            cmd.Parameters.Clear();
            cmd.Parameters.Add("@a",code);

            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)//如果有数据
            {
                dr.Read();
                end = dr["nationname"].ToString();
            }
            else
            { 
            
            
            }
            conn.Close();
            return end;
        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using 实体类_数据访问类.App_Code;
using System.Data.SqlClient;

namespace 实体类_数据访问类
{
    class Program
    {
        static void Main(string[] args)
        {
            //打印出所有信息
            while (true)
            {
                Console.Clear();//清屏
                Console.WriteLine("======================人员信息表======================");
                Console.WriteLine();
                Console.WriteLine("用户名" + "	" + "密码" + "	" + "昵称" + "	" + "性别" + "	" + "生日" + "            " + "民族");
                //实例化,先引用空间名
                SqlConnection conn = new SqlConnection("server=.;database=Data0720;user=sa;pwd=123");
                //设置数据库中的表的操作
                SqlCommand cmd = conn.CreateCommand();
                cmd.CommandText = "select * from Users";
                //执行操作
                conn.Open();
                SqlDataReader dr = cmd.ExecuteReader();
                while (dr.Read())
                {
                    Console.WriteLine(dr["username"] + "	" + dr["password"] + "	" + dr["nickname"] + "	" + (((bool)dr["sex"]) ? "男" : "女") + "	" + Convert.ToDateTime(dr["brithday"]).ToString("yyyy年MM月dd日") + "	" + dr["nation"]);
                }
                conn.Close();

                Console.WriteLine("-------------------------------------------------------------");
                Console.Write("请输入您想执行的操作（1.添加 2.删除 3.修改 4.查询某条信息 5.查询全部信息）:");
                string n = Console.ReadLine();
                

                //实例化
                UsersData udata = new UsersData();//在这个类被实例化的时候UsersData()代表的就是UsersData类中的构造函数

                if (n == "1")
                {
                    //添加
                    #region
                    //实例化
                    Users u = new Users();//构造函数是默认的，可以不写，在这个类被实例化的时候Users()代表的就是构造函数

                    Console.Write("请输入用户名：");
                    u.username = Console.ReadLine();
                    Console.Write("请输入密码：");
                    u.password = Console.ReadLine();
                    Console.Write("请输入昵称：");
                    u.nickname = Console.ReadLine();
                    Console.Write("请输入性别：");
                    u.sex = (Console.ReadLine() == "男");
                    Console.Write("请输入生日：");
                    u.brithday = Convert.ToDateTime(Console.ReadLine());
                    Console.Write("请输入民族：");
                    u.nation = Console.ReadLine();

                    //实例化  UsersData
                    udata.Insert(u);//调用udata里面的Insert()方法
                    #endregion
                }
                else if (n == "2")
                {
                    //删除
                    #region
                    Console.Write("请输入要删除的用户名：");
                    string Uname = Console.ReadLine();
                    Users u2 = udata.select(Uname);
                    if (u2 != null)
                    {
                        Console.WriteLine("已查到此用户，请执行删除！");
                        Console.ReadLine();
                        bool ok = udata.Delete(Uname);
                        if (ok)
                        {
                            Console.WriteLine("删除成功！");
                        }
                        else
                        {
                            Console.WriteLine("删除失败！");
                        }
                    }
                    else
                    {
                        Console.WriteLine("请核实用户名输入是否正确！");
                    }
                    #endregion
                }
                else if (n == "3")
                {
                    //修改
                    #region
                    Users u3 = new Users();
                    Console.Write("请输入您要修改的用户名：");
                    u3.username = Console.ReadLine();

                    if (u3 != null)
                    {
                        Console.Write("已查到此用户，请进行修改！");
                        Console.ReadLine();
                        Console.Write("请输入修改后的密码：");
                        u3.password = Console.ReadLine();
                        Console.Write("请输入修改后的性别：");
                        u3.sex = (Console.ReadLine() == "男");

                        udata.Update(u3);
                    }
                    else
                    {
                        Console.WriteLine("未查到您输入的用户名，请核实后重新输入！");
                    }
                    #endregion
                }
                else if (n == "4")
                {
                    //查一条数据 
                    #region
                    Console.Write("请输入你要查找的用户名：");
                    string Uname = Console.ReadLine();
                    Users u = new UsersData().select(Uname);
                    if (u != null)
                    {
                        Console.WriteLine("已查到此用户！");
                        Console.ReadLine();
                        Console.WriteLine("用户名" + "	" + "密码" + "	" + "昵称" + "	" + "性别" + "	" + "生日" + "            " + "民族");
                        Console.Write(u.username + "	" + u.password + "	" + u.nickname + "	" + u.sex + "	" + u.brithday + "	" + u.nation);
                        Console.ReadLine();
                    }
                    else
                    {
                        Console.WriteLine("未查到此用户信息，请核实后重新输入！");
                    }
                    #endregion
                }
                else if (n == "5")
                {
                    List<Users> ulist = new UsersData().select();
                    if (ulist.Count > 0)//如果有数据
                    {
                        Console.WriteLine("用户名" + "	" + "密码" + "	" + "昵称" + "	" + "性别" + "	" + "生日" + "             " + "民族");
                        //循环打印，用foreach
                        foreach (Users u in ulist)//遍历，把每一个数据都拿出来看一下
                        {
                            Console.WriteLine(u.username + "	" + u.password + "	" + u.nickname + "	" + u.sex1 + "	" + u.brithday1 + "	" + u.nationname);
                        }
                        Console.ReadLine();
                    }    
                }
                else
                {
                    Console.WriteLine("您的输入有误，请重新输入！");
                }

            }
            Console.ReadLine();
        }
    }
}

添加：

删除：

修改：

查询一条信息：

查询全部信息：